Though the screenplay never read more than something simple like, “characters rush to bridge to escape balrog,” Jackson added crumbling grounds in the too-deep mine, asked the characters to make life-risking leaps over an abyss, added arrow fire and even a teetering stair for one of the most edge-of-seat scenes in the flick.

The script itself said something along the lines of, “The fellowship runs from the balrog, down a staircase and across a bridge,” but director Jackson expanded on the concept based on imagery of a crumbling bridge that one of his artists composed.